The deposition and processing of refractory metal silicides has become the topic of many recent investigations due to their vital role in the future of very large scale integration (VLSI) technology. Initially, silicide films were intended to be used for the gate metallization in metal/oxide/semiconductor (MOS) devices. The next generation of silicide films will be used to shunt not only the gates of the MOS devices but the source and drain region as well, thus reducing their resistance. Silicide film structures for both the gate as well as the source and drain can be done in principle in a single processing step, giving rise to the process labelled self-aligned silicide formation. The self-aligned silicide formation process is done in a furnace sintering step by reacting the refractory metal film with the polysilicon film on top of the gate oxide and the bulk silicon at the source and drain regions, to form the refractory metal silicide film. The unreacted metal on the sidewalls is subsequently stripped away in a preferential etch that will not attack the silicide film. A serious problem with this technique as conventionally practiced relates to the fact that the diffusing species during the formation of many refractory metal silicides is silicon. Thus, during a sintering step at elevated temperatures which is required to form the desired silicide film, some silicide may form at the gate sidewall which will not strip in a preferential etch. This can result in an electrical short between the gate and the source and drain regions.
TiSi.sub.2 is a suitable refractory metal silicide for self-aligned silicide applications for two reasons. One, it is the most conductive of all the refractory metal silicides. And two, it has the lowest temperature of formation. At the same time, however, there are problems associated with the sintering step between Ti and Si. Ti happens to be extremely sensitive to oxidation and this prevents the formation of high quality films. Also, some out-diffusion of the dopant from the source and drain regions through the silicide may take place because of the high temperatures involved in the sintering step, thus leaving high resistance shallow junctions.
Along another vein, in addition to the desire to be able to deposit a refractory metal to form a high-quality refractory-metal silicide, a need exists to be able to form high quality epitaxial silicon layers on silicon substrates as well as to be able to form high-quality oxides and nitrides on silicon substrates for a variety of purposes. The subject invention proposes a way to sputter such layers in an efficient fashion and in a manner in which the formed layers are of a relatively high quality.